The miRNA biogenesis factors, p72/DDX17 and KHSRP regulate the protein level of Ago2 in human cells

MicroRNAs (miRNAs) are short (21-23nt long) RNAs that post-transcriptionally regulate gene expression in plants and animals. They are key regulators in all biological processes. In mammalian cells miRNAs are loaded into one of the four members of the Argonaute (Ago) protein family to form the RNA-induced silencing complex (RISC). RISCs inhibit the translation of mRNAs that share sequence complementarity with their loaded miRNAs. miRNA processing and miRNA-mediated gene regulation are highly regulated processes and involve many RNA-binding proteins as auxiliary factors. Here we show that the two RNA-binding proteins, p72 and KHSRP, both with known roles in promoting miRNA biogenesis, regulate the protein level of human Ago2 in transformed human cells. We determined that p72 and KHSRP influence Ago2 stability by regulating miRNA levels in the cell and that loss of p72/KHSRP results in a decrease of unloaded Ago2.